1. Field of the Invention
The present invention relates to a solar radiation amount calculation technique that calculates a solar radiation amount using an output of a solar panel.
2. Description of the Related Art
Energy management systems (EMSs), each of which is an energy control system as a part of a power system, are sorted according to the type and scale of a management target. The EMSs are classified into a home EMS (HEMS) targeted at a home, a building EMS (BEMS) targeted at a building, a factory EMS (FEMS) targeted at a factory, and a community EMS (CEMS) targeted at a community. The CEMS controls, as targets, a HEMS, a BEMS, and a FEMS within a target area, grasps a required power amount, gives an EMS as a control target a command to suppress energy consumption, and grasps the supply amount of power from the outside, thereby performing flexible and dynamic energy management.
In thermal power generation and nuclear power generation that utilize fossil, fuel (coal, oil, natural gas, oil sand, shale gas, or methane hydrate) or underground resources such as uranium as exhaustible energy, since the fuel and resources can be stored, a power generation amount is hardly affected by a power generation environment (weather and the like) (operation is conducted not to be affected). However, renewable energy (sunlight, wind power, wave/tidal power, flowing water/tides, geothermal heat, biomass, or the like), especially solar photovoltaic power generation (PV) that has been rapidly increasing in recent years is greatly affected by the natural environment, which may cause the system to be unstable. Therefore, energy management to improve the prediction accuracy of a solar power generation amount and thereby stabilize the system is required of CEMSs in the future.
As methods for solving this problem, there are three methods disclosed in JP-A-2010-249608 (Patent Document 1), JP-A-2012-124188 (Patent Document 2), and JP-A-2003-121558 (Patent Document 3). In the method of Patent Document 1, regional solar radiation amount and meteorological data are obtained from the outside to estimate a solar radiation amount, and a power generation amount of a PV array according to the solar radiation amount is predicted. In the method of Patent Document 2, a PV array power generation amount is predicted by comparing time-series data of the PV array power generation amount. In the method of Patent Document 3, a solar radiation amount is calculated from PV array power generation data acquired from a PV array, and the solar radiation amount is provided as weather information.
The method of Patent Document 1 needs an actinometer installed in the region and a device for acquiring the regional meteorological data from the outside. Therefore, extra cost is incurred for installing an EMS. Moreover, since the installation environment of a PV array varies depending on the tilt and shape of a roof, a great difference is generated between the values of individual PV arrays and the measured value of the regional actinometer. Hence, the prediction accuracy of the power generation amount generated by the PV array according to the solar radiation amount is also lowered.
On the other hand, the method of Patent Document 2 can predict a power generation amount at low cost without using another device. However, since only the comparison of fluctuation patterns of the time-series data is performed, an error in prediction of power generation amount is great. Especially, the method cannot cope with the formation or disappearance of a cloud.
The method of Patent Document 3 does not need to install a device other than a PV array, and therefore, a study was conducted to calculate the hours of sunlight using this method and predict a power generation amount by combining the method of Patent Document 1 without adding measuring instrument or acquiring additional data.
Actually, however, except for a sunny day, solar radiation changes sharply in terms of time on a day with a cloud, and a spike-like change is rapidly repeated in a short time. Therefore, when the prediction of solar radiation is performed using the solar radiation of the cloudy day as it is, the predicted value of power generation amount also rapidly increases or decreases repeatedly. When interpolation or extrapolation is performed based on such a spiky measured or predicted value and the prediction horizon is extended, the obtained result is also a spiky result, which increases an error in prediction.
In the related art in which other measured data is not used as described above, it is impossible to measure a solar radiation amount with consideration also given to the small movement of a cloud that affects a power generation amount generated by the PV array. Therefore, the accuracy of prediction of the power generation amount generated by the PV array is low.